Using Stable and Radioactive Isotopes for Assessment of Origin and Sustainable Management of Groundwater Resources

saqarTvelos mecnierebaTa erovnuli akademiis moambe, t. 11, #2, 2017 BULLETIN OF THE GEORGIAN NATIONAL ACADEMY OF SCIENCES, vol. 11, no. 2, 2017

Geophysics

George Melikadze*, Lika Chelidze**, Sopio Vepkhvadze*, Mariam Todadze*

* M. Nodia Institute of Geophysics, Ivane Javakhishvili Tbilisi State University ** E. Andronikashvili Institute of Physics,Ivane Javakhishvili Tbilisi State University

(Presented by Academy Member Tamaz Chelidze)

ABSTRACT. The paper reports on drinking water storage situation in the Eastern Georgia and recent study of underground water resources in Alazani-Iori catchment with using a hydro-geochemical and environmental isotope application. More than hundred groundwater and surface water samples were analyzed to study composition of major ions and isotopes 18O, 2H and 3H. During the field work, physical and chemical parameters of waters (temperature, pH, DO, EC) were obtained. Three groups of groundwater were identified, revealing the dominant evolution of mineralization from Northwest to Southeast, with major increase in the Shiraki area. The geochemical patterns among the groups change from Ca(Mg)/

HCO3 type in the Kvareli aquifer to Na/SO4(Cl) type in the Shiraki syncline. Variation indicated the evolution of groundwater isotopic composition on the path from the recharge area in the mountains and then through the river valley to exfiltration areas, from the 18O values more, than -8.5 ‰ V - SMOW and 2H values less than -55 ‰ V - SMOW, till 18O values between -11 and -13‰ V - SMOW and 2H less than 75 ‰ V - SMOW. Tritium concentration is decreasing from the West to the East on the territory and the smallest concentration is observed on the Shiraki plain. Almost all aquifers in the study area contain admixture of older waters with no Tritium and low 18O values. Whereas the ground waters in the Alazani valley artesian aquifers are concluded to be of a good quality they are recommended for drinking. © 2017 Bull. Georg. Natl. Acad. Sci.

Key words: stable isotopes, GMWL, water origin

More than 70% of Georgian water supply comes conditions of Georgia. These negative effects could from the groundwater (GRW). One of the biggest be the most serious in the Eastern Georgia, espe- zones of groundwater is the Eastern Georgia [1]. cially in the hydrogeological basin area of the Iori These groundwaters belong to the least surveyed river, which is known to have clearly depicted char- and exploited aquifers in Georgia. It is expected that acteristics of arid-zone and semi-desert. Preliminary global warming will have negative effect on natural meteorological data show that precipitation has sig-

© 2017 Bull. Georg. Natl. Acad. Sci. 48 George Melikadze, Lika Chelidze, Sopio Vepkhvadze, Mariam Todadze nificantly decreased in this region, which caused The Alazani valley between the Greater Cauca- depletion of underground water and natural springs. sus and the Kakheti ridge is filled with Quaternary Hence, there is a distinct tendency of processes ac- sediments and sediments of the river Alazani. It con- tively leading to desert formation. All these negative sists of sandy-gravel and clay-loam sediments, form- ecological events led to deterioration of population’s ing several water-bearing horizons down to approxi- social-economic conditions. As the negative ecologi- mately 500 m in three principal aquifers – Kvareli, cal processes become stronger, desert formation can Gurjaani and Telavi. The total thickness of sediments easily turn into an irreversible form. Understanding of the Alazani valley, lying on the surface of crystal- the GRW regime, its interactions with surface waters, line rocks, is between 2 and 4 km. which influence groundwater quantity and quality is The Garekakheti Plateau is formed by tertiary therefore of the utmost importance to secure water sediments with outcrops of Upper Jurassic rocks supply for the economy and population. (Dedoplitskaro Hill). The synclines on the Shiraki Plain Besides the traditional methods of hydrogeo- are filled by Quaternary sediments of the logical survey, mapping of the environmental and Krasnokolodski suite. They consist of argillaceous radioactive (tritium) isotopes concentration as water sands, conglomerates and gravels. The sands are tracers provide useful complementary information on partly gypsiferous. The largest Shiraki syncline is of water origin, history and contamination, thus con- considerable extension up to 50 km, and the sediments tributing to the assessment of groundwater vulner- are approximately 1000 m thick. ability and sustainability in terms of both water quan- From the hydrogeological point of view, the tity and quality [2, 3]. Alazani and Iori basins have the area of approximately Regular sampling and analyses of oxygen and 8000 sq.km. It includes the Alazani and Iori artesian hydrogen isotopes in natural waters (18O, 2H, 3H) aquifers, the adjacent aquifers of the Shiraki Plain are permanently held by International Atomic Energy synclinal and the Kakheti-range in the West-North- Agency. Therefore, it becomes common practice in west. This range and the entire Greater Shiraki Plain many countries as a part of national meteorological, are climatic boundaries between the water-abundant geological and hydrological observation systems. In Alazani basin and the water-scarce Iori basin. The contrast, the topic is new in the Caucasian region. valley is drained by the Alazani and Iori rivers. An- other important source of water is the groundwater Material and Methods from numerous boreholes and wells [5]. The origin of Study area is represented by a valley surrounded by the groundwater remains unknown. the Greater Caucasus Mountains (altitudes up to 3500 In the frame of the mentioned project more than m a.s.l.) in the north and lower Gombori Range (alti- one hundred water points (springs, boreholes, dug tudes up to 2000 m a.s.l.) in the South. From the geo- wells, rivers and lakes) were sampled during six cam- logical point of view, composition of the study re- paigns from April 2012 until October 2013. Isotopes gion is complex and contains Jurassic, Cretaceous, 18O, 2H and 3H were measured at each site. During Paleogene, Neogene and Quaternary rocks [4]. The field work, physico-chemical parameters of waters Northeastern and Northwestern slopes of the (Temperature, pH, DO, EC) were obtained by the Kakheti ridge are formed by Alazani series of Neogene WTW Multi 340i set. Samples were also taken for and Pleistocene continental sediments. Their maxi- stable isotopes’ and Tritium analyses. mum thickness is 2 km and the dominant components Isotopic composition of precipitation was stud- are gravels, conglomerates and sands. Gravels are ied on the basis of monthly composite samples from typically formed by large size boulders of sandstone Global Network Isotope in Precipitation (GNIP) and and limestone material. Global Network Isotope in Rivers (GNIR) stations,

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017 Using Stable and Radioactive Isotopes for Assessment of Origin... 49

Fig. 1. Distribution of 18O isotopes between different sites on the topo- map. located in Tianeti, Telavi, Lagodekhi, DedoplisTskaro stable isotopes (18O, 2H) were analysed in all water [6, 7]. samples from different hydrogeological groups The isotopic and hydochemical analyses were (Fig. 1). Fig. 1 reveals that modern recharge water performed in the Laboratory of Institute of Geophys- with 18O values more than -8.5 ‰ V-SMOW (Vienna ics by laser analizator Picarro L2110-I; chemical com- Standard Mean Ocean Water - is a water standard position was measured by Flame-photometer PFP7 defining the isotope composition of the fresh water) and DREL2800; Tritium analysis was performed in is fixed in the spring, river and boreholes in the left the Hacettepe University, Turkey. bank of river Alazani. These values are related with groundwaters of the Alazani series and Kvareli aqui- Theory/Calculation fer. Similar values of 18O were fixed in the spring and Groundwater sampling was generally conducted in boreholes in limestone’s aquifers located on the the NW-SE transects, i.e. from the Southern slopes DedoplisTskaro “Hill”. Telavi and Gurjaani artesian of the Greater Caucasus across the Alazani valley structures contain groundwater with heavier 18O value

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017 50 George Melikadze, Lika Chelidze, Sopio Vepkhvadze, Mariam Todadze

-50

-60

Tsnori 1 ] ‰ [ -70 H 2 δ Akhmeta Telavi Kvareli Gurjani -80 Lagodekhi Heretitskali Tsnori Sighnaghi Dedoplis Tskaro Samtatskaro Sagarejo -90 GMWL

-13 -12 -11 -10 -9 -8 -7 δ18O [‰]

Fig. 2. Isotopic composition of different groundwater samples is compared with the Global Meteoric Water Line (GMWL). between -7.5 and -8.5 ‰ V-SMOW, in the 200-500 m the “Samtatskaro” borehole, probably represents deep layer. Samples from deep boreholes in the open older waters. The rest of samples are modern water, thermal water layer (Heretitshkali, Tsnori, etc), con- which partially underwent evaporation. The Sagarejo tain paleo-waters with d18O values between -11 and - waters do not form one group. Tsnori field is charac- 13‰ V-SMOW. Similar value of 18O has the terised with changeable values of samples. The data groundwater of the Shiraki syncline and of the mid- presented point to the evolution of groundwater iso- dle part of river Iori. topic composition on its travel from the recharge area Exactly the similar picture of distribution was fixed in the mountains and through river valley to the for 2H. Modern recharge water has 2H values less exfiltration areas. The concept, which is in agreement than -55 ‰ V - SMOW; Telavi and Gurjaani aquifers with hydrogeological data of the area, is presented - between-55-65 ‰ V - SMOW; Thermal water spring also in Table 1. Fig. 2 displays the 18O  2H relation- and the Shiraki groundwater - less than 75 ‰ V- ship. It reveals that waters of almost all samples are SMOW. located along the global meteoric water line (GMWL). The above values are characteristic for the re- This is relationship between deuterium and oxygen- gional scale, but there are more variations between 18 concentrations in natural meteoric waters and in- water sources in local areas. For example, Dedoplis- dicated isotopic enrichments, relative to ocean wa- Tskaro form two groups of springs. Part of them, from ter, which display a linear correlation over the entire

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017 Using Stable and Radioactive Isotopes for Assessment of Origin... 51

Fig. 3. Spatial distribution of Tritium in the Alazani-Iori area on the topo- map range for waters, which have not undergone exces- (3-6 TU), which correspond to admixture of modern sive evaporation. recharge waters (after 1950) with old-age waters and Values of two samples, collected from the Lake for Alazani and Kvareli groundwater group, respec- Kechabi on the Shiraki Plain and the geothermal karst tively (7-11 TU), which are of modern origin. spring Heretitshkali deviate from the global meteoric Results and Discussion water line. These deviations are related to evaporation under semiarid climate conditions and to water- Complex geological, hydrogeological, hydrogeo- rock interactions in geothermal environment. chemical and isotope investigations were carried out Tritium concentration in the area is presented in in the Alazan-Iori Artesian Basin and three types of Fig. 3: it decreases from the North-West direction to hydraulic zones were revealed. South-East. The Tritium concentrations (TU units) The first type of groundwater has a total minerali- show a presence of older (recharged prior to nuclear zation up to 1.0 g/l. This corresponds to the modern tests’ ban in 1950’s) waters in samples from thermal recharge pattern with 18O values between -8.5 and - water and Shiraki groundwater group type has rela- 9.9 ‰ V - SMOW and respectively with Tritium con- tively low concentrations of tritium (0.1-1.8 TU), which tent of 7-11 TU. This type is dominant in ground- characterizes old groundwaters, recharged prior to waters of the Alazani series, Kvareli aquifer, springs the 1950ґs, including paleo-waters. Tritium concen- and in the rivers. trations increase for the Telavi and Gurjaani aquifer The second type of groundwater has a total min-

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017 52 George Melikadze, Lika Chelidze, Sopio Vepkhvadze, Mariam Todadze

Table 1. Average values of isotopic composition in precipitation, river and GRW samples and perceptual model of groundwater movement (column groundwater zone). Groundwater zone Site, source 18O average 2H average Deuterium excess [‰] [‰] average [‰] Precipitation, Telavi -7.9 -50 12.9 Precipitation, Lagodekhi -9.3 -61 14.1 River, Alazani (Shakriani) -9.4 -60 15.3 Recharge area GRW, Kvareli -9.5 -60 15.6 GRW, Lagodekhi -9.6 -61 16.1 River valley GRW, Akhmeta -8.9 -56 15.4 GRW, Telavi -8.7 -55 14.6 Exfiltration GRW, Gurjani -8.3 -53 13.3 GRW, Sighnaghi -8.4 -55 12.1 GRW, DedoplisTskaro -8.3 -55 11.7 Evaporate GRW, Shiraki 11 75 ‰ 11.5 Mixed water GRW, Sagarejo -8.9 -58 13.6 eralization between 1.0 to 2.0 g/l. Tritium concentra- Plain for alternative drinking water sources in the tions increase for the second type of GRW to 3 - 6 Shiraki region. TU. These types of waters are fixed in some parts of Conclusions the Telavi and Kvareli aquifers and in the entire Gurjaani aquifer. Isotopic composition of river water in the Alazani Third group is the most mineralized sodium chlo- valley evolves according to the global meteoric wa- ride type groundwater - covers the territory of the ter line. Available isotopic data indicate several Shiraki Plain area, contains paleo-waters with 18O groups of groundwater. Some of them probably rep- values between -11 and -13‰ V - SMOW and rela- resents older waters. The most of variables indicate tively low concentrations of tritium: 0.1 - 1.8 TU. This the evolution of groundwater isotopic composition pattern characterizes the old type of GRW, recharged on the path from the recharge area in the mountains prior to the1950ґs. The increased mineralization can and then through river valley to exfiltration areas. be explained by saline sediments of the Quaternary The isotopic composition of river Alazani near Telavi age, as a result of intense evaporation with a mini- indicate that the river is contributed mainly by mum amount of precipitation. isotopically light water from higher altitudes. Deute- Although most of the artesian boreholes are up rium excess has higher value, which is typical for to 500 m deep, their groundwaters belong to different mountain precipitation and snow in other mountain hydraulic and isotopic groups, what should be re- ranges. If the seasonal snow cover at the foothills of lated to the local stratigraphy. Groundwater analyses the Greater Caucasus does not last for a longer pe- confirmed the evolution of mineralization pattern from riod, spring rainfalls might be crucial for groundwater North-West to South-East, with a major value in the replenishment. The conjunctive use of isotopic ap- Shiraki syncline area. Tritium concentration is de- proaches demonstrates its high potential for future creasing from the West to East on the territory and water resource studies in Georgia. the smallest is observed on the Shiraki plain. Acknowledgments: The authors are grateful to Finally, the wwaters of the Shiraki plain area are the Shota Rustaveli National Science Foundation for characterized by high mineralisation and therefore financial support of the project #31/27 “Environmen- are of lower quality for drinking. It is recommended tal Isotopes Testing in Alazani-Iori Catchments (East to enhance the production of drinking waters from Georgia) for Provision of Sustainable Use of the karstic formations, such as the Dedoplitskaro Groundwater Resources”.

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017 Using Stable and Radioactive Isotopes for Assessment of Origin... 53 geofizika stabiluri da radiaqtiuri izotopebis gamoyeneba miwisqveSa wylebis warmoSobis dadgenisa da mdgradi ganviTarebisaTvis g. meliqaZe*, l. WeliZe**, s. vefxvaZe*, m. TodaZe*

*ivane javaxiSvilis saxelobis Tbilisis saxelmwifo universiteti, m. nodias geofizikis instituti, Tbilisi, saqarTvelo **ivane javaxiSvilis saxelobis Tbilisis saxelmwifo universiteti, e. andronikaSvilis fizikis instituti, Tbilisi, saqarTvelo

(warmodgenilia akademiis wevris T. WeliZis mier)

naSromSi ganxilulia aRmosavleT saqarTveloSi arsebuli viTareba, kerZod, sasmeli wylis deficiti. alazani-ioris auzis miwisqveSa wylis sistemis Seswavlis mizniT pirvelad ganxorcielda kvlevebi hidrogeoqimiuri da ekologiuri traserebis gamoyenebiT. asze meti miwisqveSa da zedapiruli wylis sinji iqna gaanalizebuli ZiriTadi ionebis Semadgenlobisa da 18O, 2H, 3H izotopebis Seswavlis mizniT. savele kvlevebisas dadginda wylis fizikur-qimiuri parametrebi (temperatura, pH, gaxsnili Jangbadi, eleqtro- gamtaroba). dadgenil iqna miwisqveSa wylis sami jgufi, gamovlinda mineralizaciis zrda CrdiloeTidan samxreTis mimarTulebiT, Siraqis sinklinSi umetesi mniSvnelobebiT. am jgufebs Soris yvarelis wyalSemkrebi auzisaTvis gamovlenilia Ca(Mg)/HCO3 tipis wylebi, xolo Siraqis wyalSemkrebi auzisaTvis ki Na/SO4(Cl) tipi. dafiqsirebuli cvli- lebebi miuTiTebs miwisqveSa wylebis izotopuri Semadgenlobis evoluciaze, mTebSi ganlagebuli kvebis arealidan mdinaris xeobebis gavliT gantvirTvis arealebisaken; Sesabamisad 18O mniSvnelobiT -8.5 ‰ V-SMOW-dan 2H mniSvnelobiT -55 ‰ V-SMOW- mde, 18O mniSvnelobiT -13‰ V-SMOW-dan 2H mniSvnelobiT 75 ‰ V-SMOW-mde. tritiumis mniSvneloba mcirdeba dasavleTidan aRmosavleTis mimarTulebiT da umciresi mniSvnelobebi fiqsirdeba Siraqis velze. wyalSemcveli horizontebis umetesoba moicavs Sereuli tipis wylebs, tritiumis nulovani SemcvelobiT da jangbadis izotopis mcire raodenobiT. alaznis xeoba Seicavs maRali xarisxis miwisqveSa wylebs da rekomendebul iqna sasmelad.

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017 54 George Melikadze, Lika Chelidze, Sopio Vepkhvadze, Mariam Todadze

REFERENCES

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Received February, 2017

Bull. Georg. Natl. Acad. Sci., vol. 11, no. 2, 2017